Telephony.



M.- JOHNSON} I TELEPHONY.

APPLIOATION FILED MAY 22, 1911.

Patented Mar. 18,1913.

3 SHEETS-SHEET 1.

M. L. JOHNSON.

TELEPHONY. APPLICATION FILED MAY 22, l911.

Patented Mar. 18, 1913.

3 SHEETS-SHEET 2.

IMPEDANCE.

j L. JOHNSON.

TELEPHONY. APPLICATION FILED MAY 22, 1911.

Patented Mai. 18, 1913.

3 SHEETS-BEBE! 3.

- @Zzaqn TI m 5&9 w

UNITED STATES PATENT MORTON L. JOHNSON, OF CHICAGO, ILLINOIS, AS SIGNOR T CORWIN'TELEPHONE MA N- UlFACTURING COMPANY, OF CHICAGO, ILLINOIS, CORPORATION ILLINOIS.

TELEPHONY.

Specification of Letters Patent. I Patent-ed 131 18,

Application filed may 22, 1911. 'Serial No. 628,779.

T 0 all whom it may concern:

Be it known that I, Mon'roNL. J oHNsoN,

citizen of the United States, residing at accompanying drawings, forming a part of this specification.

My invention relates to telephone ex change systems and, in one of its aspects, relates to those telephone exchange systems in which telephone lines extend from party line stations to an exchange and are adapted for connection with telephone lines extending to another exchange through the agency of trunks extending between the two exchanges. In order to simplify the trunking equipment I have organized a system which may generally be described as a telephone exchange system including a telephone line that extends from one exchange to a second exchange where means are provided for extending the connection of the trunk, a source of .signaling'current, means at the second exchange for applying the source of signaling current to the trunk,-'and means. atthe;

first exchange governing the aforesaid means at the second exchange and in turn governed by the apparatus at a statlon upon said line whereby the calling party at a party line station may cause the application of signaling current to the signal receiverat another station upon the same line.

I have embodied my invention in a system in which the exchange to which thetelephone line extends is provided with selecting mechanism for selecting an idle trunk extending to the second exchange where solecting mechanism is also employed for extending the idle trunk, as 'for example, by connecting it with a called party line connected with the second exchange. By means.

of my invention I am enabled to use the trunk that is employed for connecting the telephone line with these'cond exchange for conveying signaling current to the telephone line at the will of a calling partyupon said line in order that. such calling party may Another feature of my invention resides in the provision of means, exterior to the exchange with which the telephone line is connected, irrespective of the nature of such exchange, automatic or-otherwise, and irrespective of the means by which said exchange is connected with the telephone line, whether by a trunk line or directly, whereby apparatus is remove 1 from such circuit association with the li e as would interfere with the proper transmission of signaling current.

- Specifically, my intention further resides in a system, hereinafter to be described, ha'v-v switches) is employed for selectively con:

necting trunks with party lines whereby the sides of a party line may be extended to .a main exchange where he party line is further to be extended in -accordance' with automatic or semi-automatic practice; and Fig.

3 shows selecting mechanism at a main exchange for automatically effecting further extension of the party line and also for connecting a sourcvof ringing current with the party line when the called station is on the same line with a calling station, the equipment illustrated in Fig. 3 bemg't-hat of an I automatic telephone exchange to which I do not limit myself. i

I will first describe, somewhat in detail, the particular party lirie station equipment illustrated in Eig. 1 it, being understood that donot limit myself, however, to the particular equipment shown.

The telephone lineextends from the exchange to two limbs 1, 2 and, in the embodiment of the invention illustrated, is'normally connected at its two sides with the poles of a'battery 3, the side 1 being grounded and connected through the ground to the positive pole of the 'battery 3,and-the negative pole of the battery 3 being connected with the side 29f the line. The current furphone stations upon the line takes the line for use, the source of current 3 being itself then reversed so that the side 1 is charged from the negative poleof the battery and the side 2 is charged from the positive pole of the battery. The apparatus by'which the battery 3 is reversed, and which is illustrated in Fig.2, is familiar to those that are skilled in the art of automatic telephony and will be later more fully referredto.

I have shown four party line stations 'A B' C- 1) though I do not limit myselfto the number of stations that are connected with, the party line. As the invention is -illus? trated,the equipments at the four stations are identical except, if desired, the signal -receivers at the different stations may be of harmonic type to respond to wave form current of different periodicities to be selectively impressed upon the line at the exchange. The signal receiversmay be alike, if desired, in which event code signals should be employed. I

Similar parts at the different stations w11l be given similar. characters of reference, one station being specifically described. In the system illustrated, being an automatic telephone exchange system, I- have illustrated a well known type of switching mechanism at each telephone station for" operating the selecting mechanism at the exchange. In theembodiment of the invention illustrated, the switching mechanism is controlled by a well known dial mechanism that includes a spring'winding finger ring or dial 4. The lever 5 engaged by the finger at the limit of the dial stroke releases the spring actuated device that intermittently operates the circuit opening switch 6 during the return of the spring actuated mechanism to normal. It is not necessary to describe in further detail the switching mechanism that is employed to operate the selecting mechanism at the exchange and furthermore, the invention is not to be limited to the particular type of switching mechanism illustrated. It should be said, however, that it is usual, where dial mechanism is used, to employ a master switch including contacts 7 and 8, in conjunction with the switching device 6 and in serial relation therewith, this master'switch being controlled by the switch hook 9. The telephone receiver 10, when upon its switch hook, operates to depress the element 8 of the masterswitch and there open the circuit through switch 0, through the intermediation of the depressing finger 11 and the right hand'endiportio-n of the lever 12 then depressed by the finger 11.,the right hand end portion of the lever 12 being meresistance.

chemically connected with the switching element 8 by means of a strut 13. The switch hook, when depressed, causes pawl 11- to lock theidial. sistance bridge conductor at each telephone station that includes the telephone transmitter 14 having one terminal telephonically connected with the limb 10f the tele hone line, and the receiver 10 in serial re ation with the transmitter 14, the dial switch 6, andthe contacts 7 and 8.

between the sides of the telephone line is in parallel relation with another bridge conuctor which is desirably of high resistance and is preferably normally open at the contacts 15, 16. This second bridge conductor includes a magnet 17 whichis preferably polarized, and the entire resistance of this second bridge conductor is preferably.located in the magnet which may be wound, for example, to ten thousand ohms The armature of the polarized inagnetlT is preferably held in predetermined normal osition by means of a spring 18 that norma ly locks the nose or angular extension 19 of the armature beneath the nose or angular extension 20 ofthe intermediately pivoted lever 12. A spring 21 normally presses the nose 2O againstthe nose 19. The contact element 16 is mechanically connected with the finger 11 so-that said contact 16 is permitted to engage the contact 15 when the associated telephone receiver 10 at a calling station is removed from its hook, whereby the high resistance bridge conductor including the magnet 17 is closed whereupon current from the battery 3 is permitted initial fiow' overthe line sides in a direction that will enable the magnet 17 to respond and draw its armature 19 from engagement with the nose 20 of the lever 12 against the force of the spring 18 whereupon the spring 21 is permitted to swing the lever l2-in a counter clock wise direction. the finger 11 having previously been raised There is 'a' low re- 4 The normally 7 open connection which has just been traced owing to the removal of the telephone from The-high resistance shunts that include the magnet 17 do not/permit of the diversion of sufiicient current from the low resistance shunts to interfere with the control that the switching mechanism in such a, low resistance shunt at a station which has appropriated the line has over the selecting mechanism at the exchange. It is of course understood that the electro-magnet 17 is responsive only to the current that is initially impressed upon the line owing to the normal connection of the battery 3 with' said line, this magnet at other times maintaining the telephone bridge open. By

mechanism which is well understood, and

which will later be mentioned more fully, the battery 3 has its connections with the sides of the telephone line reversed so that the currentimpressed upon the line immediately after the line is taken for use is such that the magnets 17 will not respond thereto, whereby those stations upon the line that are late in seeking to take the line for use cannot appropriate the line owing to the fact that the lever 12 at any station later to seek appropriation of the line is locked by the armature of the magnet at such station, whereby the contacts 7 and 8 of the master switch cannot be engaged to close the gap in the low resistance bridge at this later station, which closure is essential to enable a station to take a line 'for use, paw-l 11 then locking the dial. While current at any station at any time may be permitted to flow through the magnet 17 at such sta-. tion, yet such magnet will not respond if the battery 3 has been reversed since the magnet will then be so energized as merely to tend to move its armature in the same direction in which such armature is pulled by 'the spring 18 without efiecting' readjustment of the parts that enter into the control of the receiver circuit and the control of the switching mechanism that governs the operation of the selecting mechanism. I therefore speak of the magnet 17 as being unresponsive to current that is caused to flow over the telephone line in a directionopposite to the normal flow of the current.

The signal receiver 22 responds to wave "form current that is preferably an alternating current and is operated in a manner which is well understood.

I have described the operation ofthe equipment at a single telephone stationin detall'under the assumption that such a station is a calling station, and under such as sumption the battery 3 is immediately re- -versed after the line has been taken for use. -W 'hen any of the stations upon the line is a called station, the battery 3 should have its normal connection with the telephone line preserved, at least until the called Sta-- tion has responded in order that the magnet 17 at the called station may respond to permit the closure of the contacts 7 and 8 thereat and thereby enable the inclusion of the telephone equipment at the called station in bridge of the telephone line.

Referring now more particularly to Fig.

2, the battery 3 has its negative pole nor--" mally connected with the side 2 of the telephone line through an energizing winding 23, the switch spring 24 and the normal contact of such spring. The positive pole of the battery 3 is connected with the side 1 the switch spring 25 andits normal con tact. lVhen the telephone line is taken for use by a calling party at one of the stations, circuit for'the battery 3 is closed at the contacts 15, 16 at that telephone station, whereupon magnet 17 at such station is operated with results which have been described. Later, the contacts 7 and 8 at the line appropriating station are engaged to close the low/resistance shunt at such appropriating station, whereupon current from the battery 3 is increased sufiiciently to energize the winding 23 (this winding not having been previously operatively en'- ergized owing to the presence of the high resistance magnet 17 in circuit therewith) to cause the armature 26 to be attracted. The armature 26, in being attracted, pushes the contact 27 into engagement with the normal contact of the switch spring 25, thereby to bring the energizing winding 28 -fro m the grounded normal contact of the switch sprmg 25 throughthe winding 28 matures 29 and 30 are attracted with the result that the battery 3 has its connections with thesides of the telephone line reversed, these connect-ionsbeing then traceable from the side 1 of the telephone line, the contacts 31 that are closed by the armature 30,the switch 56 and its normal contact, the switch and its normal contact, the upper winding of magnet 46 (the illustration of the battery 3 being repeated many times for the sake of clearness) to the negative pole of the battery, the positive pole of the battery connection which may be traced through the contact 32 closed by the armature 30; the lower armature switch of relay -and its normal contact, the winding of relay 45, the armature switch'58, the lower winding of relay 46 to ground. Battery 3 is thus reversed instantly upon the closure of the contacts 7 and 8 at a calling station with the results which have been described. This association of the battery and telephone line is preserved during the time the receiver at the calling station is free of its hook owing to the establishmentof a..locking cir- 3, the winding 33, the contacts 38 when closed upon the operation of armature 30, the upper armature switch of relay 62 to the grounded contact of the latter armature switch. 3

ofthe telephone line through ground and' The equipmentthus far described contains into a closedlocal circuit that may be traced to the grounded battery 3, whereby the a-rbeing connected with the line side 2 by a cuit through the locking winding 33 which j may be traced from the'grounded battery novel characteristics formin the subject matter of my oo-pending app ication Serial No. 628,777, filed'May 22, 1911, but it is to be understood that while I prefer the equipment just described, I do not limit myself thereto. y Y

.Eaoh party line station low resistance bridge conductor includes a key 39 adapted when depressedto introduce a resistance 40, which may be of three thousand ohms, in

what was previously the low resistance cated and the exchange where the selecting mechanism is located for further extcndmg the trunk line, it being understood that the stations upon the party line whose sides extend into the first exchange are equipped with. apparatus whereby such party line may select an idle trunk line 1 2 .By

- means of the relayinechanism illustrated at E the three conductors that usually intervene between the line switches and the first selectors are replaced by the two conductors 1 2 a result which is very important where trunk lines intervene between ,dis

tinct exchanges, particularly where such exchanges are wide distances apart. For the sake of clearness, I will ,for the present omit a description of the relay equipment illustrated at. E and will assume that the party line has been continued from the line switch shown in Fig. 2 to the first selector shown at the leftof Fig. 3, whereafter I will describe theequipment whereby the selected section 1 2 of the party line is interposed between the party lineproper. and said first selector. Referring now more'particularly to Fig. 3, l have employed the first selector,

indicated at the middle of the figure, for

cnabling'thc application of calling current to. a calling party line, but it is to be understood that I do not limit myself to any particular switching mechanism entering into the line extending selecting mechanism for including the calling party line in circuit re;- lation with asource of current, nor do I limit myself to the transfer of ringing current over the talking sides of the party line. The selector shown in Fig. 3 is or a type I which is well known by those skilled in the art..and is a form of mechanism that is installed by the Automatic Electric (,hni'ipany.v

As is well known, this selector has wipers which swingin horizontal planes and which are vertically adjust-able so as to move in different levels, bank or waiting contacts being located in these levels which are connected with conductors that, extend to connectors directly or through the.intermediation of other selectors, whereby called lines are automatically connected with calling lines. The wipers of the selector shownin Fig. 3 are marked 41, 42 and 43 and these wipers are caused to swing in the selected level to suit the connection that they are to effect. One or more of the levels in which these wipers moveincludes bank contacts that are associated with sources of signaling current In the embodiment-of the invention illustrated code signaling is not employed, the signal receivers at the party line stations being responsive to currents of differcnt character. For example, the signal receiver 22 at, station A may respond to alternating current of sixteen cycles, the signal receiver at station B may respond to alternating current ofthirty-three cycles, the signal receiver at station 0 may respond to alternating current of fifty cycles, and the signal receiver at station D may respond to alternating current of sixty-six cycles. If

the invention is thus to be embodied, that is if the signal receivers are to be responsive to currents of different character, then there should be a plurality of levels of waiting or bank contacts associated with-sources of ringingcurrent of diflerent character, the contacts in each of these levels being separately connected with a plurality of generators producing current of similar character so that some generator producing current of desired character may be available to enable a calling party line station to signal another station upon the same line. In Fig. 3 I have illustrated but one set of waiting contacts 1 4 and 43 in one level, a single set 0 waiting contacts 41 42 and 43 in the next level, a single group of contacts 41?;42 and 43 in the next level. and a single group ofcontacts 41*, 42 and 43 in the next level. i I have shown but one generator 44 in connection with the level containing the contacts" 41 ,42 and 43 it being understood that other groups of waiting contacts in this level are similarly associated with similar generators 44. I have not. illustrated any equipment in association with the bank contacts of the remaining levels, it being understood. in the embodiment of the invention illustrated, that the generators associated with the first level produce alternating current of sixteen cyclcs, the generators associated with the contacts of the next level producing alternating current of thirty-tlnee' cycles, the gcncraters associated with the contacts of the next level producing alternating current of fifty cycles, and the generators associated with the contacts of the next level producioo ing alternating current of sixty-six cycles. The calling party line party may select the level containing the waiting contacts that are associatedwith the calling generators producing current of the frequency or othercharacter suited to the operation of the signal receiver 22 at the station upon the party line that is to be called. Having caused the wipers 41, 42 and 43 to occupy the desired level, these wipers are stepped around until wait-ing contacts associated with an unemployed generator 44 are encountered, the mechanism and circuits by which idle waiting contacts are engaged and busy waiting contacts are passed over being so well known as not to require explanation.

It is assumed that any of the stations B, C, D is a calling party line station and station A is the party line stationupon the same line to be called. The calling station, insuch case, selects the level containing the bank contacts 41 42, and 43 and itis assumedthat these contacts which are illustrated in Fig.3 were previously free for selection and are engaged by the wipers 41, 42.

and 43 for the purpose of associating the generator 44, previously unemployed, with the party line. The wipers stopping upon these waiting contacts cause the establishment of a circuit through the relays 45 and 46 and the inclusion of thebattery in such circuit relation with the party line as to'have the side 1 connected with a positive battery pole and the side 2 connected with a negative battery pole in order to enable the party at the called party line station to bring his telephone into circuit relation with the party line. The source ofringing current 44 has terminals in the form of the alternate contacts'of armature switches of theringingmagnet 47 whose circuit includes a switch 48 periodically closed and opened by a revolving cam 49. The circuit of the ringing magnet 47 also includes a switch 50 that is closed through the agency'of the armature switch of the ;1;elay 46 and the magnet 51 in direct association with the switch 50. As will more-fully appear,'switch 50. is mamtained closed during the time the telephone "bridge atthe calling party line station is closed whether such bridge includes the resistance 40 or, does not include such' resist-' ance, the relay 46 being suitably "adjusted.

for this purpose. The relay 45, however. is, adiustcdstodrop its armature when the resistance 40 at a calling party line station is included in the telephone bridge, whereby the circuitpreviously established through the relay 52 is opened and the switch 53 controlled by vthe relay 52 is closed; During the time that the generator is upon the line, the

armature switches of the magnet 47 are "removed from their-normal contacts so that the circuit of'the relay 46 is then open. The

switch 50 is maintained closed, however, ow:-

ing to the establishment of an alternate circuit for the relay 51 which may be traced from the grounded battery 3 through the winding of the relay 51 to the'uppermost armature switch of the magnet 47 and the grounded contact then engaged by said uppermost armature switch.

Having thus generally indicated the operations that are governed at the station end of the party line, I will now describe the relaying functions of the relay equipment illustrated at E through which party line station equipment operates upon the equipment connected with the party line by means of the selector shown in Fig. 3 for the purpose of effecting the application of ringing current to a calling party line.

-Each trunk line 1 2 has a relay equipment E individual thereto and the line switch individual to each party line is adapted to select and appropriate an idle trunk line 1 2 together with the idle relay mechanism E individual to; such trunk line, the" switch of a calling line, as were the three conductors of trunk 'lines in prior equip ments- An idle set of conductors 1 2f, 3 having become operatively associated. with the line switch of a calling line, circuit is established through the relay 46 of the relay mechanism E, which .circuit'may be traced from the battery 3 through the upper winding at 46 the switch 55, the switch 56 and its normal contact, the switch 31 to the side 1 of the calling party line, thence across the telephone bridge at the calling party line station to theside 2 of the calling partytelephone line, the switch 32, the conductor 2 the switch 57 and its alternate contact, the relay device 45 the switch 58, thence through the lower coil of the re lay device 46 to theground. The armature switches of the relay device 46 are consequently moyed whereby a bridge is established between the conductors 1 2 of the trunk individual to the selected relay mechanism E for the purpose of controlling the selector switch shown in Fig. 3, this bridge being broken at 59 each time the circuit is interrupted at the calling party line station,'whereby the selector is operated just as thoughv it were directly connected with the" telephone bridge at the calling party line station. The bridge established across the sides 1 2 of the selected trunk includes an impedance 60 for the purpose of preventi g loss of voice current transmission. The relay device'61' has a compa'nion coil that-is included in circuit with thebafttery 3 and the upper armature switch of a relay device 62, which latter device has circuit closed therethrough, in order to op crate its armature, by the relay device 46 this circuit Ibeing' traceable through the battery 3, the winding of relay device 62, the

switch 63 to ground, the relay device 62 be: ing sluggishso that the interruption occasioned 1n the telephone bridge'at the calling station by the operation of the dial. switchwill not be followed by the release gized. hen however, the selector shown in Fig. 3 has selectedan idlegenerator i t, the battery 3 is reversed whereupon the magnet 61 is effectively energizedto operate its armature switches and open the contacts atand 58 and establish contacts at' 64' and 65 whereby the battery 3,which was previously reversed from normal connection by theline switch of the calling line, is re stored line, in which the side- 1 is connected with .to normal connection with the party the positive pole of the battery and the side 2 is connected with the negative pole of the battery whereby the calling party line party is enabled to remove his telephone from its switch hook and include it in bridge of the line during the time the key 39 at the calling station is depressed, since the exclusion bridge would permit the diversion of enough current from the battery 3 to prevent the operation of the relay 1-7 at the called station. 1 v I H During the operation of the dial, the magnet 62 is energized and remains energized as has been stated during which time another magnet 66 is energized by a circuit established through the battery 3 and the lower armature switch of the magnet. 62. The magnet 66 operates sluggishly so that it also is not effectively denergized during the operation of the dial. The bridge containing the impedance 60 is broken at the normal contact of .the upper armature switch of the magnet 66. A substitute bridge is established between the sides 1 2 which may be traced from the side 1 through the upper armature switch of relay 67 and its normal contact,-t-he upper armature switch of relay 66 and its alternate contact, the armature switch 59, the intermediate armature switch of magnet 67 and. its contact 57 to the side 2 This bridge is broken at 59 each time each time the low resistance bridge'conductor at the calling station is broken, whereby the selector shown at the left in Fig. 3 is operated in the usual mannerr When the operation of the dial has been completed at the calling station, magnet 66 is included the .dial mechanism breaks the low resistance bridge conductor at the calling telephone station so that the circuit of the battery 3 (Fig. 3) is broken:

in open circuit owing to the continued re moval of the intermediate armature switch restoring the bridge 1 previously traced through the impedance 40. The idle generator 44 havin been selected, current is trans- 'mitted there rom over the party line as a of relay 46 from its normal contact, thus cons'equenpe of the energization of the magnet 47 duexto the concurrent closure of the switches at 48, 53 and 50. The relay 45 is controlled in its operation by the relay 4:5,

the relay 45 being responsive to current that is permitted to flow through the low resistance bridge at the calling station, but dropping its armature when the'key 39 at the call ng station is depressed for the purpose of including the resistance 40 in circuit with the relay 45 When the armature of the relay &5 is dropped, a ground is placed upon the side 1 of the trunk line by way of the armature switch of relay. 45 and the upper armature switch of magnet 67, as a consequence of which relay 45 (Fig. 3) is shunted so that it is permitted to drop its armature whereby the circuit previously established through the relay52' by way of this latter armature is opened. Switch 53 of relay 52 is then closed to close one gap in the circuit. of the ringing magnet 47. The gap 50 in this circuit of the ringing magnet is constantly closed owing to the circuit established therethrough that may be traced from the battery 3 through the winding of the magnet 51 controlling the switch M50 and either the armature switch of magnet 46 g (which magnet is energized when the ringing'magnet 47 is deenergized whether the resistance 40. at the calling station is in or out of circuit), or the uppermost armature switch of the ringing magnet t7 when said ringing magnet is energized. The ringing current is consequently applied to the sides 1 2 of the trunk line and the sides otth e party line at the will of the calling party during. the time-the key 39 at the callin station is depressed, the calling current being interrupted at 47 periodically in accordance with the best accepted practice. I provide a relay 68 at the s'tationwhcre the relay mechanism E is located for the purpose of freeing the party line from connection with any parts of the selecting mechanism and elements associated therewith that would intcrfere with the proper transmission of signaling current from the selected generator 44.- This relay 68' is desirably included in bridge of the trunk conductors 1 2 and is preferab1y energized by a shunted portion of the winging current, said relay being designed .TSO 'as to keep its armature attracted during the. presence of ringing current upon the line. 'VVhen the relay 1 68 is included in bridge and iscaused to respond to alternating current, I desirably include a' oon'denser 69 in series therewith and in the same bridge for the purpose of preventing the improper shunting of battery current. As I have employed the relay 68, it serves when energized to establish circuit through magnets 67 and which may be traced from the battery 3 through the windings of said magnets and the armature switch of relay 68 when actuated by said relay. The upper armature switches of the mag'nets'67 and 70 are provided with connected alternate contacts so that when said magnets are energized the trunk side 1 and the conductor 1 are directly metallically connected. The lower armature switches of the magnets 67 and 70 are also provided with connected alternate contacts whereby the trunk side 2 and the conductor 2 are directly connected when these magnets are energized. In this way the condensers 71 and 72 (that are serially included respectively between the conductors 1 1 and the conductors 2 2 by the normal contacts of the armature switches of the magnets 67 and 7 0 during the time that ringing current is absent from the line and for the purpose of preventing the flow .of battery current between the stationsshown in Figs; 2 and 3) are excluded from the path of the ringing current, a desirable result when wave form current of differing frequency is to be selectively placed upon the party line. Other apparatus at the station shown in Fig. 2 which is connected with the party line when ringing current is absent, is also removed by the operationof the armature switches of the magnets 67 and 70 alsofor the purpose of preventing interference with the function of the ringing current. In order to prevent the possibility of the relay 68 responding to the interruptions occurring at the dial switch of the callingparty line subscriber, I include the lowermost armature switch of the magnet. 66 in serial relation with the relay 68 so that when the magnet 66 is energized as it is during the operation of the dial owing to its sluggish nature as previously described, the bridge containing the relay 68 is open. As another incidental feature of the equipment illustrated, the lowermost armature switch of therelay 67 serves when actuated to close circuit through the magnet 62 Whose upper armature switch thereupon establishes a circuit through look ing coil 33 by way of the contacts 38 to prevent the line switch from being. restored to normal when the magnets 67 and 7 Q are energized.

As the invention is illustrated, the called "partyfcan not secure telephonic connection with the party line until the battery current flows in normal direction over ,the line,

which condition occurswhen the-circuit through the ringingmagnet 47 is opened at 48. Lihowever, do not limit myself to this characteristic which is simply preferred-for engineering reasons. When thecalled party responds, a low resistance bridge is established across the sides of the party line through the telephone at the called party line station, whereby the magnet 45 is energized and the magnet 52 is consequently energized in order to open the circuit of the ringing magnet 47- at 53 during the presence of the low resistance shunt across the lineat the called station under the assumption that the calling party has released his calling station may include the resistance 40 for the purpose of enabling sufficient current to pass through the magnet 17*. at the called station. When the relay 46 is energized, circuit is closed through the magnet 54 by way of the grounded armature switch of therelay 46 and the contact of such switch then engaged, the winding of the relay 54 to the grounded battery 3 I When the ringing current is applied to the'party line, circuit for the relay 54 is closed through the uppermost armature switch of the magnet 47, the winding of the relay 54 and thel grounded battery 3. The armature of relay J 54 is thus constantly attracted so as to place a guarding potential or condition upon the contact 41 to prevent another calling line. station from appropriating the contactsl42 43 that are in service- This guardingpotential also prevents the selector and asso.

ciated switches from releasing in the manner" well known.

- Iprefer to connect the ringingcurrent witli the trunk line by means of selecting.

mechanism that-is also of service in connecting the trunk line with a continuation, but I do not limit myself to this characteristic since animportant feature of my invention resides in the provision of therelay mechanism at E having control over the means for applying the calling current. to" the line, the relay mechanism at E being llO responsive to the operation of the dial mechanism at the calling station'and replacing this dial mechanism in directcontrol of the application of ringing current to the party line so that the dial mechanism serves indirectly to control the application ofringing current to the line.

That feature of my invention embracing the relay 68 is of importance irrespective of the means by which the generator is connected with the-line, whether such means be automatically operatedor otherwise, this feature of my invention. also being of im-,

portance irrespective of the manner in which a calling party secures connection with the exchange, whether such connection is automatically effected or otherwise. This feature of the invention is also-of importance whether or not the calling and called partieslare upon the same party line since results are secured by clearing interfering apparatus from the line when signaling currenzlis being transmitted over the line.

imy application Serial No. 628,77 8 filed May 22 1911, I have broadly claimed a system wherein the selecting mechanism operates-to apply ringing current to a called party line. The prior art is exemplified by British Patent No. 1298 of 1910.

While Ihave herein shown and particularly described a telephone exchange system employing apparatus for'connccting called lines with calling lines, I do not wish to be limited to such system nor to the precise detailsof apparatus and circuit connections illustrated as changes may readily be made without departing from the spirit of my invention. v

Having thus described my invention I claim as new and desire to secure by Letters Patent the following 1. A telephone exchange system including a line connecting a plurality of telephone stationswith an exchange: trunks extending from said exchange to another exchange; selecting mechanism at the first exchange for selectively connecting a trunk with said telephone line; selecting mechanism at the second exchange for extending -.the selected trunk; a source of signaling current adapted to be connected with the trunk by the selecting mechanism at the second exchange; and mechanism at the first exchange for governing the operation of the selecting mechanism at the second exchangc'and in turn governed at a party line station whereby a calling party at a party line station may cause the application of a signaling current to the signal receiver at another station upon the same line.

2. A telephone exchange system including a line connecting a plurality of telephone stations with an exchange; trunks extending from said exchange to another exchange; selecting mechanism at the first exchange for selectively connecting a trunk with said telephone line; a source of signaling-cui'rent; meansat the second exchange for connecting it with the selected trunk; and mechanism at the first exchange for governing the operation of said means at v the second exchange and in turn governed at a party line station whereby the calling "party at a party line station may cause the application of signaling current to the signal receiver at another station upon the same line.

' 3. A telephone exchange system including a telephone line extending from a plurality of stations to an exchange; a trunk extending from this exchange to a second exchange where means are provided for extending t e connection of the trunk; a source of signaling current; means at the second exchange for applying the source of signaling current to the trunk; and means at the first exto an exchange; a trunk line extending from this exchange toasecond exchan e and having equipment interfering witi the proper transmission of signaling current; a source of signaling current; means governed at the second exchange for controlling the application of signaling current to the line; and means at the first exchange for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current.

5. A telephone exchange system'including a telephone line extending from a station to an exchange; a' trunk line extending from this exchange to a second exchange and having equipment interfering with the proper transmission of signaling current; a source of signaling current at the second exchange; means at the second exchange and there governed for controlling the application' of signaling current to the trunk and the line connected therewith; and means atthe first exchange for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current;

6. A telephone exchange system'including a telephone line extending from a station to an "exchange; a trunk line extending from this exchange to a second exchange and having equipment interfering with the proper transmission of signaling current; a source of signaling current; means governed at the second exchange for controlling the application of signaling current to the line; and means at the first exchange for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current, there being means at the second exchange for governing this latter means.

7. A. telephone exchange system including a telephone line extending from a station to an exchange; a trunk line extending source of signaling current at the second exchange; means at the second exchange and there governed for controlling the application of signaling current to the trunk and the line connected therewith; and means at the first exchange for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current, there being means at the second exchange for governing this latter means.-

8. A telephone system including a telephone line connecting a telephone station with an exchange and having equipment interfering with the proper transmission of signaling current; means at the exchange for applying signaling current to the line; and means for removing apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current.

9.-A telephone exchange system including a telephone line extending from a sta-- tion to an exchange; a trunk line extending from this exchange to a second exchange and having equipment interfering with the proper transmission of signaling current;

a source of signaling current; means governed at the second. exchange for controlling the application of signaling current to the line; and means at the first exchange and responsive to the signaling current for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current.

10. A telephone exchange system including a telephone line extending from a station to an'exchange; a trunk line extending from this exchange to a second exchange and having equipment interfering with the proper transmission of signaling current; a source of signaling current at the second exchange; means at the second exchange and there governed for controlling the application of signaling current to the trunk and the line connected therewith; and means at the first exchange and responsive to the signaling current for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current.

11. A telephone exchange system including a telephone line extending from a station to an exchange; a trunk line extending from this exchange to a second exchange and having equipment interfering with the proper transmission of signaling current;

a source of signaling current; means governed at the second exchange for controlling the application of signaling current to the line; and means at the first exchange and responsive to the signaling current for removing trunk line apparatus from such circuit association with the line as would interfere with the proper transmission of signaling current there bein means at the second-exchange for governing this latter means.

12. A telephone exchange system includ ing a telephone line extending from a station to an exchange; a trunk line extending from this exchange to a second exchange with the line as would interfere with the.

proper transmission of signaling current, there being means at the second exchange for governing this latter means.

13. A telephone system including a telephone line connecting a telephone station with an exchange and having equipment interfering with the proper transmission of signaling current; means at the exchange for applying signaling current to the line; and means responsive to the signaling current for removing apparatus from such cir cuit association with the line as would interfere Withthe proper transmission of signaling current.

In witness whereof, I hereunto subscribe my name this fourth day of May A; D.,' 1911.

MORTON L. JOHNSON.

Witnesses:

MARGARET D. Ross, G. L. CRAGG.

topics at this patent may be obtained for in cents each, by addreldhg the Commissioner of Patents,

Washington, D. 0. 

